The present invention relates to a soft cannula and methods for insertion into, removal from, and use within a patient's body cavity.
During many types of arthroscopic operations a rigid cannula is inserted into a patients body to provide access for medical instruments. The rigidity of the cannula creates several problems: large insertion points are generally required to accommodate the circumference of the rigid cannula; the circumference available for manipulating the instruments is strictly limited; the gasket or ribbing on the outer circumference of the cannula provides very little traction; and apparatus for sealing the cannula tends to leak.
U.S. Pat. No. 5,573,517 and U.S. Pat. No. 5,532,611 (the "Bonutti et al. references") are directed to cannulas that are inserted through tissue in an unexpanded condition. Once inserted, the inserted cannula is expanded radially to allow for instrument passage. Each Bonutti et al. cannula uses a plurality of wires or longitudinally extending members that extend through the length of the of the cannula to expand an elastic sheath. To use a Bonutti et al. cannula, a narrow trocar is inserted into the cannula which are then jointly inserted into a small incision in the patient's epidermis. A small tubular insert is then inserted between the cannula and the trocar to expand the cannula radially and allow the trocar to be removed. Additional tubular inserts of progressively increasing diameters are then inserted into the cannula. A final full sized tube is left in place within the expanded cannula so that medical instruments may be inserted there through. Although the Bonutti et al. cannulas may provide an expanding circumference that allow for a small insertion point, problems such as the strict limitation of the circumference available for manipulating instruments, little traction, and leakage are not addressed. Further, it is questionable as to whether the Bonutti et al. Cannulas are significantly flexible.